/* ----------------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:		arm_q15_to_q7.c
*
* Description:	Converts the elements of the Q15 vector to Q7 vector.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated.
* ---------------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupSupport
 */

/**
 * @addtogroup q15_to_x
 * @{
 */


/**
 * @brief Converts the elements of the Q15 vector to Q7 vector.
 * @param[in]       *pSrc points to the Q15 input vector
 * @param[out]      *pDst points to the Q7 output vector
 * @param[in]       blockSize length of the input vector
 * @return none.
 *
 * \par Description:
 *
 * The equation used for the conversion process is:
 *
 * <pre>
 * 	pDst[n] = (q7_t) pSrc[n] >> 8;   0 <= n < blockSize.
 * </pre>
 *
 */


void arm_q15_to_q7(
    q15_t* pSrc,
    q7_t* pDst,
    uint32_t blockSize)
{
	q15_t* pIn = pSrc;                             /* Src pointer */
	uint32_t blkCnt;                               /* loop counter */

#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */
	q31_t in1, in2;
	q31_t out1, out2;

	/*loop Unrolling */
	blkCnt = blockSize >> 2u;

	/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
	 ** a second loop below computes the remaining 1 to 3 samples. */
	while(blkCnt > 0u) {
		/* C = (q7_t) A >> 8 */
		/* convert from q15 to q7 and then store the results in the destination buffer */
		in1 = *__SIMD32(pIn)++;
		in2 = *__SIMD32(pIn)++;

#ifndef ARM_MATH_BIG_ENDIAN

		out1 = __PKHTB(in2, in1, 16);
		out2 = __PKHBT(in2, in1, 16);

#else

		out1 = __PKHTB(in1, in2, 16);
		out2 = __PKHBT(in1, in2, 16);

#endif //      #ifndef ARM_MATH_BIG_ENDIAN

		/* rotate packed value by 24 */
		out2 = ((uint32_t) out2 << 8) | ((uint32_t) out2 >> 24);

		/* anding with 0xff00ff00 to get two 8 bit values */
		out1 = out1 & 0xFF00FF00;
		/* anding with 0x00ff00ff to get two 8 bit values */
		out2 = out2 & 0x00FF00FF;

		/* oring two values(contains two 8 bit values) to get four packed 8 bit values */
		out1 = out1 | out2;

		/* store 4 samples at a time to destiantion buffer */
		*__SIMD32(pDst)++ = out1;

		/* Decrement the loop counter */
		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

#else

	/* Run the below code for Cortex-M0 */

	/* Loop over blockSize number of values */
	blkCnt = blockSize;

#endif /* #ifndef ARM_MATH_CM0 */

	while(blkCnt > 0u) {
		/* C = (q7_t) A >> 8 */
		/* convert from q15 to q7 and then store the results in the destination buffer */
		*pDst++ = (q7_t)(*pIn++ >> 8);

		/* Decrement the loop counter */
		blkCnt--;
	}

}

/**
 * @} end of q15_to_x group
 */
